Ultraviolet light is a well known means of disinfection and photo-oxidation and this system has been utilized to disinfect or to sterilize water. It is also well known that ultraviolet radiation between 200 and 300 nanometers is most effective in reducing harmful micro-organisms.
Pertinent prior art patents include:
1. U.S. Pat. No. 4,861,484 issued to N.N. Lichtin, et al. on Aug. 29, 1989. This patent describes a process used to produce an effluent suitable for discharge into the terrestrial environment from organic waste. It is a two step batch process in which the device used is a transition metal catalyst and the system requires expendable organic solvents and an oxidizer such as peroxide or ozone. It is noted in the patent that granular activated carbon ("GAC") is a filter material which is useful for the purification of potable water and industrial waste water. Regeneration of the contaminated GAC is by thermal volatilization in which the organic materials previously absorbed into the surface Of the GAC are desorbed by heat and oxidized at high temperature. Limitations of this method include a loss of GAC due to oxidation and attrition, and the cost of energy in heating the GAC to temperatures of about 800.degree.-850.degree. C. The patent also describes off-line chemical regeneration of exhausted GAC in which contaminants of the GAC are desorbed into an organic solvent, which is then treated in a fluidized state with a solid catalyst, an oxidizer, and photoenergy.
In the system, a transitional solid metal catalyst is added and removed as a slurry. The system also requires a gravitational field to facilitate catalyst removal as well as expendable organic solvents and an oxidizer.
2. U.S. Pat. No. 4,798,702 issued to R.E. Tucker on Jan. 17, 1989 discloses a plurality of ultraviolet light sources arranged relative to a fluorinated ethylene propylene tubing which partially transmits ultraviolet light. The tubing is coiled into a helical form around an ultraviolet germicidal source for sterilizing a water solution which flows through the tubing. In this patent it is noted that pipes or tubing made of a fluorinated ethylene propylene copolymer are capable of transmitting ultraviolet radiation over an extended period of time without undergoing photochemical deterioration. Polytetrafluoroethylene also has non-stick properties so that pipes do not cloud with residue. While a smaller pipe favors a better kill, the volume of fluid being sterilized is reduced. A larger pipe increases volumetric flow but reduces the bacterial reduction. In short, the residence time of the fluid media and the intensity of the lamps must be correlated to reach acceptable levels of bacterial kill.
3. U.S. Pat. No. 4,661,264 issued to P.R. Goudy, Jr. on Apr. 28, 1987 utilizes an ultraviolet light laser beam for disinfecting flowing water. The laser beam can be pulsed. The patent notes that water sterilization has been accomplished in the past by flowing water over the surface of a series of ultraviolet bulbs.
4. U.S. Pat. No. 4,219,415 issued to N.A. Nassef on Aug. 26, 1980 discloses a device which employs microwaves as an energy source for treating organic waste products. The patent describes placement of organic waste material on a bed of solid particles of activated carbon. Liquid passes over the bed of solid activated carbon particles and percolates downwardly through the activated carbon particles. Microwave irradiation provides sterilization. When the carbon particles are exhausted they are replaced. This is basically a batch process utilizing a large number of moving parts and expendable components, and which requires a gravitational field to operate properly.
Sterilization or disinfection of water using an ultraviolet light is an established art, as noted heretofore. Filtration of water through filter beds of granulated activated charcoal is also used for purification of water. As used herein granulated activated charcoal may be sometimes referred to as GAC, carbon or charcoal. The treatment of water by filtration through filter beds of granulated activated charcoal to obtain potability tends to remove organic and inorganic contaminants and to some extent micro-organisms from a water solution. However, the granulated activated charcoal filter beds in collecting the contaminants also become a source of contamination in time. This occurs because over a period of time the organic contaminants tend to occlude all of the available carbon surfaces which limits the ability of the filter bed to remove incoming contaminants. The combination of organic substances and the carbon surfaces to which they are absorbed also provides an excellent situation for the poliferation of micro-organisms. Efforts to limit fouling of granulated activated charcoal filter beds with chemicals or thermal means have met with little success. Consequently, fouled granulated activated charcoal filter beds must be periodically removed from a system and replaced with fresh activated carbon. Periodic replacement of charcoal filter beds heretofore has been a customary solution to fouled charcoal filter beds. In any number of instances it is desirable to prolong the life and usefulness of the charcoal filter bed.